i installed mallory 4309 regulator today, but didnt seem to work. fuel came out of the top of the carb, had the adjustment screw as low as it would go just to see if there was a drop in pressure, but no.

You probably dont have a big enough return line. I had the exact same problem. The stock lines just are not big enough. You need either 5/16 or preferred 3/8 from the regulator to the pump. You will also need to adapt the line to the sending unit if you use 3/8 because its 5/16 up there.

i have 3/8 line from the pump to the reg. and 3/8 back to the tank. I have to do what to the sending unit?? thanks

do you have the small vacuum port on the 4309 plugged into vacuum or not? I used the stock 3/8 supply line and adapted the 5/16 return line and my 4309 works great. and do you have a pressure gauge hooked up?

no i dont have the vacume port hooked up. it doesnt even seem like anything is going into the return line though....

Hook up the vacuum line to a full vacuum source and see if it then works. I've done two of them now, one needed vacuum, the other did not. Not sure why the difference, but either way it worked.

I had the same problem.
You have to turn the adjustment screw counter clockwise to decrease pressure to the carb and if your return is coming out the bottom of the regulator then you can try to take the spring out of the regulator. Take the 4 allen screws out and below the adjustment screw there will be a spring. Take it out then put the regulator back together. I had to do this to get mine to stop pulsating the pressure. All my return lines were correct size and I had to do this to get things straighten out. Good Luck